Only a subset of your Exchange mailbox items are synchronized in Outlook 2016 or 2013

Symptoms

Consider the following scenario:

You're using Microsoft Outlook 2016 or Outlook 2013.

You're connected to an Exchange Server mailbox.

Notes

If you're running Outlook 2016, this account might be your primary mailbox or another mailbox to which you have delegate access or another permission. This might be an additional, shared, or auto-mapped mailbox, or public folders.

For more information about this issue in Outlook 2016 related to shared mailboxes or public folders, see the following article in the Microsoft database:

3140747 Only a subset of items are synchronized in shared mailboxes or public folders in Outlook 2016

If you're running Outlook 2013, the account must be your primary account.

In this scenario, the email folders for these mailboxes may show item counts that are lower than expected. Additionally, older items seem to be missing, and you receive the following message and hyperlink at the bottom of the list of items:

There are more items in this folder on the server

Click here to view more on Microsoft Exchange

This message is shown in the following screen shot.

Additionally, if you search for email items in your mailbox, the search results may display the following text at the bottom of the results:

Showing recent results...

More

This message is shown in the following screen shot.

If you click the More link, additional items that meet your search criteria are displayed in the search results. This occurs because Outlook retrieves the additional items from your mailbox on the server that's running Exchange Server.

Note This behavior can also occur in the RSS Feeds folder in your Exchange mailbox.

Cause

This behavior occurs because the Cached Exchange mode Mail to keep offline setting is configured to a value other than All. For example, the following screen shot shows a profile that's configured to use Cached Exchange Mode and the Mail to keep offlinesetting is set to a default value of 12 months.

In the default configuration, depending on the size of your hard disk, Outlook synchronizes only 1, 3, or 12 months of email to your Offline Outlook Data (.ost) file from the Exchange server.

If your Mail to keep offline setting is set to 12 months and you have email items in your Exchange mailbox that are older than 12 months, those items reside only in your mailbox on the server. Therefore, if you can't connect to the Exchange server, you may be unable to retrieve items outside the range that's specified by the Cached Exchange Mode synchronization setting until you reconnect with the server.

Note This setting does not affect the number of items that are synchronized with folders of the following types:

Calendar

Contacts

Tasks

Journal

Notes

Outbox

Shared or delegated (only for Outlook 2013)

More Information

To reduce the effect of the Outlook offline data file (.ost), the default number of months that are configured for your profile varies by the size of your hard disk. The following table provides the different default values for different hard disk sizes.

Hard disk size

Default value for "Mail to keep offline"

Less than or equal to 32 GB

1 month

Greater than 32 GB, but less than 64 GB

3 months

Equal to or greater than 64 GB

12 months

If you have to change the number of selected months of email to synchronize with your cached mode .ost file, follow these steps:

Start Outlook.

On the File tab, click Account Settings, and then click Account Settings.

On the E-mail tab, double-click your Microsoft Exchange account.

In the Change Account dialog box, drag the Mail to keep offline slider to the desired number of months or to All to synchronize all email messages.

Click Next.

Click OK when you're prompted to restart Outlook to complete the configuration change.

Click Finish.

Restart Outlook.

Working Offline

If you don't have connectivity with the Exchange server, the following message is displayed in a folder if there are older items on the server that were not synchronized with your .ost file:

There are more items in this folder on the server

Connect to the server to view them

This message is shown in the following screen shot.

Under similar conditions, if you search for items in your mailbox and you don't have connectivity with the Exchange server, the following message is displayed underneath the search results:

Server unavailable. <x> months of results shown.

In this message, <x> represents the value that's configured for the cached mode Mail to keep offline setting.

An example of this message is shown in the following screen shot.

Feature Administration through Group Policy

The cached mode Mail to keep offline setting is maintained in the Outlook profile settings in the Windows registry. If you want to administer this setting by using Group Policy, you can use the Group Policy templates. These are available from the following Microsoft websites, depending on your version of Office:

The Group Policy template files for Outlook 2016 are Outlook16.admx and Outllk16.adml. The files for Outlook 2013 are Outlk15.admx and Outlk15.adml. If you use Group Policy to manage this setting, the following registry data is used by Outlook:

Key: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\x.0\Outlook\Cached ModeDWORD: SyncWindowSettingValue: integer value (Decimal) specifying the number of months (use only the following values)

Note The Outlook 2016 user interface (UI) lets you set the Mail to keep offline setting to the additional values of 3 days, 1 week, and 2 weeks. The May 3, 2016, update for Outlook 2016 allows you to set these additional values by using the SyncWindowSettingDays registry data. For more information about how to configure Outlook 2016 with these additional values, see the following article in the Microsoft Knowledge Base: